Gas burners are commonly used on the cooktops of household gas cooking appliances including e.g., range ovens and cooktops built into cabinetry. A significant factor in the performance of gas burners is their ability to withstand airflow disturbances in the surroundings, such as room drafts, rapid movement of cabinet doors, and most commonly rapid oven door manipulation. For appliances which comprise both an oven and cooktop, manipulation of the oven door can be particularly troublesome because rapid openings and closings of the oven door can produce respective under-pressure and over-pressure conditions within the oven cavity. These pressure changes may cause rapid expansion and/or contractions in the structures. As a result, a large amount of air passes through or around the gas burners with e.g., rapid opening or closing of the oven doors. Similarly for built in cooktops, pressure changes due to rapid manipulation of surrounding cabinets may result in large amounts of airflow through or around the gas burners.
Such surges of air around the gas burners, due to pressure disturbances in the surroundings, are detrimental to the flame stability of the burners and may cause extinction of the flames. This flame stability problem is particularly evident in sealed gas burner arrangements, which lack an opening in the cooktop surface around the base of the burner so as to prevent spills from entering the area beneath the cooktop.
The inherent cause of this flame instability is the low pressure drop of the fuel/air mixture passing through the burner ports of a typical burner used on the cooktop of an appliance. Although there is ample pressure available in the fuel, the pressure energy is used to accelerate the fuel to the high injection velocity required for primary air entrainment. Relatively little of this pressure is available at the burner ports. A low pressure drop across the ports allows pressure disturbances propagating through the ambient to easily pass through the ports, momentarily drawing the flame towards the burner head and leading to thermal quenching and extinction.
An additional problem is that rapid adjustments of the fuel supply to a gas burner from a high burner input rate to a low burner input rate often will cause flame extinction when the momentum of the entrained air flow continues into the burner even though fuel has been cut back, resulting in a momentary drop in the fuel/air ratio, and causing extinction.
A solution to the above-described problem is the use of a stability chamber as described e.g., in U.S. Pat. No. 5,800,159, commonly owned by the assignee of the present invention. In one embodiment, the stability chamber is formed from baffles extending radially outward from a burner throat and in a widening manner towards a simmer flame port. Primary burner ports are positioned proximate the simmer flame port. Tangentially fed inlets to the stability chamber are positioned proximate the burner throat. The burner is able to maintain the simmer flame at both low and high settings so that the simmer flame can relight the flame at the primary burner ports when needed.
A portion of the stability chamber is formed by a burner cap placed over the top of the burner. For proper burner operation, proper placement of the burner cap onto the burner body is necessary. In one conventional construction, the burner cap is maintained in place on the burner body by a plurality of pegs that extend from the bottom of the burner cap into the burner body. These pegs are welded to the cap—adding expense and complexity to manufacture. To avoid the use of such pegs, another conventional construction uses an annular groove formed in the burner cap that aligns with projections in the burner so as to properly position the burner cap.
Unfortunately, the annular groove can prevent or impede the proper functioning of a burner that is equipped with a stability chamber. More particularly, the groove can overlap with the baffles or walls of the stability chamber. This can cause several problems. For example, excessive fuel may be fed into the chamber through the groove. For smaller burners, the grooves may also overlap gas inlet ports on the baffles, which can lead to flashback of the flame into the burner.
Accordingly, a burner having one or more features for properly locating the burner cap onto the burner body would be useful. A burner having such features without interfering with the proper operation of a stability chamber of the burner would be particularly beneficial.